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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** NetX Secure Component */
/** */
/** Transport Layer Security (TLS) */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SECURE_SOURCE_CODE
#include "nx_secure_tls.h"
#if (NX_SECURE_TLS_TLS_1_3_ENABLED)
/* Defined in nx_secure_tls_send_serverhello.c */
extern const UCHAR _nx_secure_tls_hello_retry_request_random[32];
#endif
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_secure_tls_process_serverhello PORTABLE C */
/* 6.1.9 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function processes an incoming ServerHello message, which is */
/* the response to a TLS ClientHello coming from this host. The */
/* ServerHello message contains the desired ciphersuite and data used */
/* in the key generation process later in the handshake. */
/* */
/* INPUT */
/* */
/* tls_session TLS control block */
/* packet_buffer Pointer to message data */
/* message_length Length of message data (bytes)*/
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* _nx_secure_tls_check_protocol_version Checking incoming TLS version */
/* _nx_secure_tls_ciphersuite_lookup Lookup current ciphersuite */
/* _nx_secure_tls_process_serverhello_extensions */
/* Process ServerHello extensions*/
/* [nx_secure_tls_session_client_callback */
/* Client session callback */
/* */
/* CALLED BY */
/* */
/* _nx_secure_dtls_client_handshake DTLS client state machine */
/* _nx_secure_tls_client_handshake TLS client state machine */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 Timothy Stapko Initial Version 6.0 */
/* 09-30-2020 Timothy Stapko Modified comment(s), added */
/* priority ciphersuite logic, */
/* verified memcpy use cases, */
/* fixed renegotiation bug, */
/* resulting in version 6.1 */
/* 10-15-2021 Timothy Stapko Modified comment(s), fixed */
/* TLS 1.3 compilation issue, */
/* resulting in version 6.1.9 */
/* */
/**************************************************************************/
UINT _nx_secure_tls_process_serverhello(NX_SECURE_TLS_SESSION *tls_session, UCHAR *packet_buffer,
UINT message_length)
{
#ifndef NX_SECURE_TLS_CLIENT_DISABLED
UINT length;
UCHAR compression_method;
USHORT version, total_extensions_length;
UINT status;
USHORT ciphersuite;
USHORT ciphersuite_priority;
NX_SECURE_TLS_HELLO_EXTENSION extension_data[NX_SECURE_TLS_HELLO_EXTENSIONS_MAX];
UINT num_extensions;
#if (NX_SECURE_TLS_TLS_1_3_ENABLED)
USHORT tls_1_3 = tls_session -> nx_secure_tls_1_3;
NX_SECURE_TLS_SERVER_STATE old_client_state = tls_session -> nx_secure_tls_client_state;
tls_session -> nx_secure_tls_client_state = NX_SECURE_TLS_CLIENT_STATE_IDLE;
#endif
/* Parse the ServerHello message.
* Structure:
* | 2 | 4 + 28 | 1 | <SID len> | 2 | 1 | 2 | <Ext. Len> |
* | TLS version | Random (time + random) | SID length | Session ID | Ciphersuite | Compression | Ext. Len | Extensions |
*/
if (message_length < 38)
{
/* Message was not the minimum required size for a ServerHello. */
return(NX_SECURE_TLS_INCORRECT_MESSAGE_LENGTH);
}
/* Use our length as an index into the buffer. */
length = 0;
#if (NX_SECURE_TLS_TLS_1_3_ENABLED)
if (tls_session -> nx_secure_tls_1_3 && tls_session -> nx_secure_tls_local_session_active)
{
/* Client has negotiated TLS 1.3 and receives a ServerHello again.
* Send an unexpected message alert. */
return(NX_SECURE_TLS_UNEXPECTED_MESSAGE);
}
#endif
/* First two bytes of the server hello following the header are the TLS major and minor version numbers. */
version = (USHORT)((packet_buffer[length] << 8) + packet_buffer[length + 1]);
length += 2;
/* Verify the version coming from the server. */
status = _nx_secure_tls_check_protocol_version(tls_session, version, NX_SECURE_TLS);
if (status != NX_SUCCESS)
{
return(status);
}
/* Set the protocol version to whatever the Server negotiated - we have checked that
we support this version in the call above, so it's fine to continue. */
tls_session -> nx_secure_tls_protocol_version = version;
#if (NX_SECURE_TLS_TLS_1_3_ENABLED)
if (tls_session -> nx_secure_tls_1_3 &&
(NX_SECURE_MEMCMP(_nx_secure_tls_hello_retry_request_random, &packet_buffer[length], NX_SECURE_TLS_RANDOM_SIZE) == 0))
{
/* A HelloRetryRequest is received. */
if (old_client_state == NX_SECURE_TLS_CLIENT_STATE_HELLO_RETRY)
{
/* A second HelloRetryRequest is received. */
return(NX_SECURE_TLS_UNRECOGNIZED_MESSAGE_TYPE);
}
else
{
tls_session -> nx_secure_tls_client_state = NX_SECURE_TLS_CLIENT_STATE_HELLO_RETRY;
}
}
else
#endif
{
/* Set the Server random data, used in key generation. First 4 bytes is GMT time. */
NX_SECURE_MEMCPY(&tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_random[0], &packet_buffer[length], NX_SECURE_TLS_RANDOM_SIZE); /* Use case of memcpy is verified. */
}
length += NX_SECURE_TLS_RANDOM_SIZE;
/* Session ID length is one byte. */
tls_session -> nx_secure_tls_session_id_length = packet_buffer[length];
length++;
if ((length + tls_session -> nx_secure_tls_session_id_length) > message_length)
{
return(NX_SECURE_TLS_INCORRECT_MESSAGE_LENGTH);
}
/* Session ID follows. */
if (tls_session -> nx_secure_tls_session_id_length > 0)
{
NX_SECURE_MEMCPY(tls_session -> nx_secure_tls_session_id, &packet_buffer[length], tls_session -> nx_secure_tls_session_id_length); /* Use case of memcpy is verified. */
length += tls_session -> nx_secure_tls_session_id_length;
}
/* Finally, the chosen ciphersuite - this is selected by the server from the list we provided in the ClientHello. */
ciphersuite = (USHORT)((packet_buffer[length] << 8) + packet_buffer[length + 1]);
length += 2;
/* Find out the ciphersuite info of the chosen ciphersuite. */
status = _nx_secure_tls_ciphersuite_lookup(tls_session, ciphersuite, &tls_session -> nx_secure_tls_session_ciphersuite, &ciphersuite_priority);
if (status != NX_SUCCESS)
{
#if (NX_SECURE_TLS_TLS_1_3_ENABLED)
if (tls_session -> nx_secure_tls_1_3)
{
return(NX_SECURE_TLS_1_3_UNKNOWN_CIPHERSUITE);
}
#endif
return(NX_SECURE_TLS_UNKNOWN_CIPHERSUITE);
}
/* Compression method - for now this should be NULL. */
compression_method = packet_buffer[length];
/* There are no supported compression methods, so non-zero is an error. */
if (compression_method != 0x00)
{
return(NX_SECURE_TLS_BAD_COMPRESSION_METHOD);
}
length++;
/* Padding data? */
if (message_length >= (length + 2))
{
/* TLS Extensions come next. Get the total length of all extensions first. */
total_extensions_length = (USHORT)((packet_buffer[length] << 8) + packet_buffer[length + 1]);
length += 2;
/* Message length overflow. */
if ((length + total_extensions_length) > message_length)
{
return(NX_SECURE_TLS_INCORRECT_MESSAGE_LENGTH);
}
if (total_extensions_length > 0)
{
/* Process serverhello extensions. */
status = _nx_secure_tls_process_serverhello_extensions(tls_session, &packet_buffer[length], total_extensions_length, extension_data, &num_extensions);
/* Check for error. */
if (status != NX_SUCCESS)
{
return(status);
}
#if (NX_SECURE_TLS_TLS_1_3_ENABLED)
if (tls_session -> nx_secure_tls_1_3 != tls_1_3)
{
/* Server negotiates a version of TLS prior to TLS 1.3. */
return(status);
}
#endif
/* If the server callback is set, invoke it now with the extensions that require application input. */
if (tls_session -> nx_secure_tls_session_client_callback != NX_NULL)
{
status = tls_session -> nx_secure_tls_session_client_callback(tls_session, extension_data, num_extensions);
/* Check for error. */
if (status != NX_SUCCESS)
{
return(status);
}
}
}
}
#ifndef NX_SECURE_TLS_DISABLE_SECURE_RENEGOTIATION
#ifdef NX_SECURE_TLS_REQUIRE_RENEGOTIATION_EXT
#if (NX_SECURE_TLS_TLS_1_3_ENABLED)
if (!tls_session -> nx_secure_tls_1_3)
#endif /* NX_SECURE_TLS_TLS_1_3_ENABLED */
{
if ((tls_session -> nx_secure_tls_renegotation_enabled) && (!tls_session -> nx_secure_tls_secure_renegotiation))
{
/* No "renegotiation_info" extension present, some clients may want to terminate the handshake. */
return(NX_SECURE_TLS_RENEGOTIATION_EXTENSION_ERROR);
}
}
#endif /* NX_SECURE_TLS_REQUIRE_RENEGOTIATION_EXT */
if ((tls_session -> nx_secure_tls_local_session_active) && (!tls_session -> nx_secure_tls_secure_renegotiation_verified))
{
/* The client did not receive the "renegotiation_info" extension, the handshake must be aborted. */
return(NX_SECURE_TLS_RENEGOTIATION_EXTENSION_ERROR);
}
tls_session -> nx_secure_tls_secure_renegotiation_verified = NX_FALSE;
#endif /* NX_SECURE_TLS_DISABLE_SECURE_RENEGOTIATION */
#ifdef NX_SECURE_TLS_CLIENT_DISABLED
/* If TLS Client is disabled and we have processed a ServerHello, something is wrong... */
tls_session -> nx_secure_tls_server_state = NX_SECURE_TLS_SERVER_STATE_ERROR;
return(NX_SECURE_TLS_INVALID_STATE);
#else
#if (NX_SECURE_TLS_TLS_1_3_ENABLED)
if ((tls_session -> nx_secure_tls_1_3) && (old_client_state == NX_SECURE_TLS_CLIENT_STATE_IDLE))
{
/* We have selected a ciphersuite so now we can initialize the handshake hash. */
status = _nx_secure_tls_handshake_hash_init(tls_session);
if(status != NX_SUCCESS)
{
return(status);
}
}
if (tls_session -> nx_secure_tls_client_state != NX_SECURE_TLS_CLIENT_STATE_HELLO_RETRY)
#endif
{
/* Set our state to indicate we sucessfully parsed the ServerHello. */
tls_session -> nx_secure_tls_client_state = NX_SECURE_TLS_CLIENT_STATE_SERVERHELLO;
}
return(NX_SUCCESS);
#endif
#else /* NX_SECURE_TLS_SERVER_DISABLED */
/* If Server TLS is disabled and we recieve a serverhello, error! */
NX_PARAMETER_NOT_USED(tls_session);
NX_PARAMETER_NOT_USED(packet_buffer);
NX_PARAMETER_NOT_USED(message_length);
return(NX_SECURE_TLS_UNEXPECTED_MESSAGE);
#endif
}
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